As is well known in the art, brass is an alloy composed principally of copper, lead and zinc and is widely used in a variety of applications in which it comes into contact with substances intended for human consumption. Brass has been widely used for plumbing fittings, bronze alloy and a host of other applications. Perhaps the most widespread application of brass is its use in the manufacture of faucets, valves, fittings and related products intended for use in delivering potable water within a commercial or residential structure. In that application, brass alloys are composed primarily of copper and zinc, with relatively small amounts of lead having been added to render the brass workable and machinable.
Such machinability is desirable in that it facilitates finishing of the components of faucets, valves, fittings and related products and cutting of threads and the like.
It is well known that lead atoms, because of their atomic size, are larger than copper or zinc and, as a result, lead exhibits a relatively low solubility in solid solution in brass alloys. That, in turn, promotes the tendency of lead to precipitate in lead-rich regions dispersed throughout brass alloys. The tendency toward precipitation is particularly notable near the surface of such brass components. That leads to the advantage of improving the machinability of the brass adjacent to the surface thereof, but, at the same time, increases the tendency of lead present on the surface to leach into water.
For many years, the amount of lead leached into foods and liquids from modern lead-containing plumbing was generally regarded as low enough that it presented no substantial risk to persons ingesting foods and liquids coming in contact with such plumbing and like brass components. However, recent standards have significantly limited the amount of permissible leaching of lead and lead exposure at both the state and federal levels. One such example is the Safe Drinking Water Act, amended in 1988 to limit lead in solders and fluxes to 0.2% and to limit lead in public water supply pipes and fittings to 8%.
Similarly, efforts have been underway to limit the amount of lead found in food or water. California, for example, has promulgated regulations limiting lead exposure of an individual to less than 0.5 micrograms per day. On the Federal level, the EPA, in 1991, restructured the standard of lead in drinking water from 50 parts per billion to 15 parts per billion.
While the amount of lead that can be leached from brass plumbing components is generally low, it is nonetheless possible that the amount of lead that can be leached from such components may exceed current or planned standards. It has been proposed that standards be made even more stringent so that lead is omitted totally from the brass alloy or that the brass be treated so that minimum quantities of lead may be leached from such brass components.
It has also been proposed to control lead by chemical treatment to cause the lead to precipitate from water or to change its oxidation kinetics. To that end, it has been suggested that lead may be eliminated or minimized by controlling the pH of water containing trace amounts of lead using alkaline treating agents such as calcium oxide, calcium chloride and alkali metal hydroxides, carbonates and bicarbonates. It has also been proposed to employ alkaline phosphate salts and silicates to minimize corrosion. Either of those treatment steps, when used alone, may not be effective in water at some pH levels or such treatments, when used alone, may require high concentrations and extended periods of time to assure effectiveness.
Various other techniques have been used in the prior art to minimize the leaching of lead into drinking water. For example, it has been suggested that brass faucets, valves, fittings and related products can be treated in a copper chloride bath maintained at a low pH. Unfortunately, however, the effectiveness of that treatment is somewhat erratic, and the low pH's required can represent a health hazard to workers. Similarly, other copper treatments such as treatment with copper acetate have likewise been proposed, but those techniques are expensive and may be difficult to operate, particularly in terms of the removal of copper ions from waste waters.
It is accordingly an object of the present invention to provide a simple and inexpensive process for the treatment of brass components, such as faucets, valves, fittings and related products, to reduce leachable lead when the component is exposed to water.
It is a more specific object of the invention to provide a method for the treatment of brass components which is also effective in the treatment of red brass along with yellow brass.
It is yet a further object of the invention to provide a method for the treatment of brass components to reduce leachable lead therefrom which is simple and inexpensive to operate and which is effective in meeting current regulatory standards.
It is yet a further object of the invention to provide a method for the treatment of brass components which has the capability of providing dramatically reduced lead leachate test results in the form of "Q Statistics," determined in accordance with NSF International Standard 61, Section 9 which is used as the current standard by which lead content of potable water is determined.